1. Field of the Invention
The present invention relates to an image processing apparatus for use in an image recording apparatus such as a digital copying machine or the like, in which an image on a document is read and stored once. The stored image information may then be read out and printed. Particularly, the present invention relates to an image processing apparatus for use in an image recording apparatus of the so-called multi-function type having an image copying function, an image communication function as a facsimile machine, a function as a printer for outputting information from a host computer, a personal computer, etc.
2. Discussion of the Related Art
Recently, with the spread of personal computers and word processors, etc., reproducible image information has become copious and diverse. Consequently, copying machines generating higher quality copies have been manufactured. In addition, copying machines have been made that provide a variety of functions, for example, selection of the number of copies to be made and reduction/enlargement.
Other functions have also been required in a copying machine. For example, an electronic recirculating document handler (hereinafter abbreviated to "electronic RDH") function in which each of a plurality of documents are copied onto a desired number of sheets, provided that the documents are sorted properly. A bookbinding function has been implemented in which images of a plurality of documents are suitably edited and copied in a manner so that images of two documents are copied on each of opposite surfaces of each sheet of recording paper so as to divide each surface into two pages. Subsequently, all the sheets of recording paper on which images of all the documents have been copied are stacked. Lastly, the stack of sheets of recording paper are bound at the center thereof and doubled into one booklet in which the copies of the documents are arranged in the order of pages.
Copying machines have also been required to function as an image communication system (i.e. a facsimile machine), and as a printer for outputting information from a host computer, a personal computer, etc.
Conventionally, digital copying machines have been made that incorporate the above functions. In a conventional digital copying machine, documents are set in an automatic document feeder (hereinafter abbreviated to "ADF"), and the documents are automatically and successively fed by the ADF onto a platen of the copying machine so that the image on each document is read by a scanner and stored in a storage device after it is converted into an electric signal. As shown in FIG. 10, image information read by means the scanner is supplied to a compressor 102 through a multiplexer (hereinafter abbreviated to "MPX") 100 and an input interface 101. The image information supplied to the compressor 102 is compressed by the compressor 102 and then stored in a hard disk 103.
However, since the image transfer rate to the hard disk 103 is low compared to that of the input interface 101 and the compressor 102, it is difficult to transfer the image information compressed in the compressor 102 directly to hard disk 103.
Accordingly, a buffer memory 104 for temporarily storing the image information is provided between the compressor 102 and the hard disk 103 so that, image information is stored in the hard disk 103 with an image information transfer rate that is synchronized by the buffer memory 104 with the storing rate of the hard disk 103.
The above image processing apparatus is arranged so that the image information stored in the hard disk 103 is read out through buffer memory 104. The read-out image information is then expanded by an expander 105. The expanded image information is then subject to secondary processing, as necessary, by means of an image output terminal (hereinafter abbreviated to "IOT") 106, and then the image is recorded and outputted.
In FIG. 10, the reference numeral 107 designates a CPU for controlling the operation of the MPX 100, the input interface 101, the compressor 102, etc.
As described above, the digital copying machine can act as an image communication system (i.e. facsimile machine) and as a printer for outputting information from a host computer, a personal computer, etc. In this digital copying machine, therefore, not only image information supplied from a scanner but also image information supplied from a facsimile machine through a telephone line, information supplied from a host computer, a personal computer, etc., are selectively switched by means of the MPX 100 so as to be inputted in parallel through the input interface 101.
Image information supplied from a facsimile machine, host computer, personal computer, etc., is supplied through input interface 101. This image information is then compressed by compressor 102. The compressed image information can be simultaneously processed in parallel through the buffer memory 104.
In this manner, buffer memory 104 is capable of storing in parallel, under time division, not only image information supplied from a scanner but also image information supplied from a facsimile machine, a personal computer. To this end, the whole storage capacity, for example, 5 MByte, is divided into storage regions in accordance with various functions, for example, 3 Mbyte for a scanner, 1.5 MByte for a facsimile equipment, and 0.5 MByte for a personal computer.
In the case of the above described conventional digital copying machine, the following problem is encountered. That is, as noted above, the above digital copying machine can function as a facsimile machine, a printer for outputting information from a host computer, a personal computer, etc., in addition to functioning as a copier. Accordingly, the storage region of buffer memory 104 of the image processing apparatus is predeterminedly divided so as to be distributed for scanner use, for facsimile use, for personal computer use, etc. Thus, when image information of a document is read in through a scanner, if the data of the document is read with a low compression ratio to the compressor 102, the amount of image information transferred from compressor 102 to buffer memory 104 is reduced because the storage region portion of buffer memory 104 assigned to the scanner may be full.
In this case, if the read-in operation for the image of the document is continued, image information of the read-in document may be lost because the storage region portion of the buffer memory 104 assigned to the scanner is full. Therefore, in order to overcome this problem the document read-in operation by means of a scanner must be interrupted until a margin is created in the storage region portion of the buffer memory 104 assigned to the scanner. Further, when the document read-in operation is to be restarted, the document on which the read-in operation has been interrupted must be set in the ADF again to be reread. Consequently the document read-in operation becomes difficult.
Further, the document compression ratio of the compressor 102 varies depending on the kind of documents. Also, the rate of use of the storage region portion of the buffer memory 104 assigned to the scanner varies in accordance with the kind of the document to be read in by a scanner. Thus, when document data having a high compression ratio is read in, only a small quantity of the storage region of the buffer memory 104 is used. Consequently, the buffer memory cannot be used efficiently.
In order to solve the former problem, a buffer memory having a sufficiently large storage capacity is provided in advance as the buffer memory 104 to prevent interruption of the document read-in operation because of insufficient storage capacity for the scanner. In this case the problem occurs that the buffer memory 104 becomes expensive to make because of its large capacity. Therefore, it is difficult to reduce the cost of the image processing apparatus. Further, when document data with a high compression ratio is read in, large portions of the buffer memory 104 remain unused for scanner use. Thus, the buffer memory 104 cannot be used efficiently.